SAN FRANCISCO -- Traffic delays along several of the Bay Area's most heavily traveled freeway corridors declined last year but region-wide congestion reached its highest level since 2000, according to a study released Wednesday.

Officials from the Metropolitan Transportation Commission and the California Department of Transportation, which conducted the annual study, attributed the increased congestion to several years of steady job growth and the fact that congestion data was measured in 2007 with greater precision thanks to an expanded data-gathering effort.

The transportation officials said that while this year's congestion numbers may drop under the weight of $4-a-gallon gasoline, rising carpool and transit use, a weak real estate market and other factors, the region experienced 161,700 vehicle hours of delay during the morning and afternoon commute periods on an average weekday during 2007.

They said that figure is second only to the 177,600 hours recorded in 2000, at the height of the dot.com boom.

Speaking at a news conference at MTC headquarters in Oakland, Caltrans District 4 Director Bijan Sartipi said the most notable among the list of congestion hot spots that experienced a reduction in delay in 2007 was the morning commute on westbound Interstate Highway 80 from Hercules to the Bay Bridge.

Sartipi said that while the busy stretch once again topped the list of the region's most congested freeway locations, delays along the corridor fell 9 percent in 2007 to 11,100 daily vehicle hours of delay from the 12,230 hours of delay recorded on an average day in 2006.

Sartipi said the drop indicates improvements like the new FasTrak configuration at the Bay Bridge toll plaza are having a beneficial impact on backups along that corridor.

He said other factors, such as rising FasTrak use, fuel prices that climbed from an average of $2.66 for a gallon of regular in January 2007 to $3.39 by December, and a rising number of workers commuting via transit and carpools during the year, also may have played a role in the reduction of morning congestion on that freeway segment.

The annual list of the 10 worst congestion hotspots has two newcomers.

One is the southbound morning commute along Interstate Highway 880 from Marina Boulevard in San Leandro to the Route 92 interchange in Hayward, which climbed all the way to No. 8 on the list from No. 26 last year.

The other is the afternoon trip on southbound U.S. Highway 101 from Great America Parkway in Santa Clara to North 13th Street/Oakland Road in San Jose, which rose to the No. 10 position from No. 14 in 2006.